The 3' terminal region of the rubella virus positive strand RNA, referred here as cis-acting element (CAE), is implicated in initiating the negative strand RNA synthesis. Sequence analysis of the CAE showed that there is a putative TATA box which is surrounded by GC rich sequence. To determine whether this element, in DNA form has a capability to initiate transcription, a 3' end 165 bp NarI/EcoRI fragment from the Rubella virus cDNA was cloned upstream to a chloramphenicol acetyltransferase *CAT) gene. The expression of the CAT activity was dependent on the presence of CAE and the SV40 enhancer. Primer extension analysis of the CAT mRNA showed that the initiation of transcription is 34 bp downstream from the putative TATA box. DNA-gel shift analysis revealed that three specific nuclear-protein complexes were formed with the CAE and the binding sites for these proteins are between nucleotides -44 to - 108. Using primers specific for the CAE, we were able to amplify a 120 bp fragment from the Vero76 and the COS-1 cell genomic DNA in a polymerase chain reaction (PCR). DNA sequence comparison of the 120 bp genomic fragment and the rubella virus CAE revealed an overall similarity of about 43% and a regional similarity of about 51-55% at the 5' and 3' ends respectively. The 120 bp has 72-79% similarity with the mouse immunoglobulin germline D-J-C and the kappa J-C region at the 5' and the 3' ends respectively. Currently studies are in progress to isolate and characterize the cellular homologue of rubella virus CAE. Analysis of the cellular homologue of rubella virus CAE. Analysis of the cellular homologue of Rubella virus CAE can shed some light on the pathogenicity of the virus.